Compound 39, 2,5-bis(4-hydroxy-3,5-dimethoxyphenyl)-3,4-
(dihydroxymethyl)tetrahydrofuran. To an ice-cold solution of 38
(0.12 g, 0.243 mmol) in toluene (5 mL) was added DIBAL-H
(2.5 mL, 1.5 M in toluene, 11.0 eq.) over 3 min while stirring. The
solution was kept stirring over an ice–water bath for another 1
h before ethanol was slowly added to quench the excess reagent.
The resultant mixture was transferred to a separatory funnel with
ethyl acetate (100 mL) and washed with 3% aqueous HCl (100 mL)
and saturated NH4Cl solution (50 mL). The ethyl acetate solution
was dried over anhydrous MgSO4. Evaporation under reduced
pressure gave crude 39 (0.096 g, 0.22 mmol, 90%), which was used
directly for the preparation of 5b.
12 C. Crestini and D. S. Argyropoulos, J. Agric. Food Chem., 1997, 45,
1212–1219.
13 F. Lu and J. Ralph, Chem. Commun., 2002, 90–91.
14 K. Freudenberg, Science, 1965, 148, 595–600.
15 K. Freudenberg and A. C. Neish, Constitution and Biosynthesis of
Lignin, Springer-Verlag, Berlin/Heidelberg/New York, 1968.
16 P. Karhunen, P. Rummakko, J. Sipila¨, G. Brunow and I. Kilpela¨inen,
Tetrahedron Lett., 1995, 36, 4501–4504.
17 K. Syrja¨nen and G. Brunow, J. Chem. Soc., Perkin Trans. 1, 1998,
3425–3429.
18 K. Syrja¨nen and G. Brunow, J. Chem. Soc., Perkin Trans. 1, 2000,
183–187.
19 L. L. Landucci, S. Luque and S. A. Ralph, J. Wood Chem. Technol.,
1995, 15, 493–513.
20 L. L. Landucci, J. Wood Chem. Technol., 1995, 15, 349–368.
21 M. Tanahashi, H. Takeuchi and T. Higuchi, Wood Res., 1976, 61, 44–53.
22 K. V. Sarkanen and A. F. A. Wallis, J. Chem. Soc., Perkin Trans. 1,
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Compound 5b, 3,4-bis(acetoxymethyl)-2,5-bis(4-hydroxy-3,5-
dimethoxyphenyl)tetrahydrofuran. Acetylation of 39 with acetic
anhydride–pyridine (1 : 1) followed by selective deacetylation in
pyrrolidine gave the target compound 5b in 85% overall yield.
23 F. Lu and J. Ralph, J. Agric. Food Chem., 1997, 45, 4655–4660.
24 K. Lundquist, ‘Acidolysis’, in Methods in Lignin Chemistry, ed. S. Y.
Lin and C. W. Dence, Springer-Verlag, Heidelberg, 1992, pp. 287–300.
25 C. Lapierre, ‘Application of new methods for the investigation of lignin
structure’, in Forage Cell Wall Structure and Digestibility, ed. H. G.
Jung, D. R. Buxton, R. D. Hatfield and J. Ralph, American Society of
Agronomy, Crop Science Society of America, Soil Science Society of
America, Madison, WI, 1993, pp. 133–166.
26 J. Ralph and F. Lu, J. Agric. Food Chem., 1998, 46, 4616–4619 .
27 K. Li and R. F. Helm, J. Agruc. Food Chem., 1995, 43, 2098–2103.
28 J. Ralph, J. M. Marita, S. A. Ralph, R. D. Hatfield, F. Lu, R. M. Ede,
J. Peng, S. Quideau, R. F. Helm, J. H. Grabber, H. Kim, G. Jimenez-
Monteon, Y. Zhang, H.-J. G. Jung, L. L. Landucci, J. J. MacKay,
R. R. Sederoff, C. Chapple and A. M. Boudet, ‘Solution-state NMR
of lignins’, in Advances in Lignocellulosics Characterization, ed. D. S.
Argyropoulos, TAPPI Press, Atlanta, GA, 1999, pp. 55–108.
29 J. Ralph, J. Nat. Prod., 1996, 59, 341–342.
Compound
5bM,
3,4-bis(acetoxymethyl)-2,5-bis(3,4,5-
trimethoxyphenyl)tetrahydrofuran. Methylation of 5b with
methyl iodide and potassium carbonate in acetone at room
temperature overnight produced the final diaryltetrahydrofuran
model compound 5bM in 95% yield.
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